Mechanically powered flashlight
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A mechanically powered flashlight is one of several varieties of flashlights that do not need replacement of batteries, or recharging from an electrical source, but are powered directly or indirectly by mechanical movement by the user. The light source can be a miniature incandescent bulb or light-emitting diode.
Various types exist with regard to the way work is applied:
- squeezing a handle
- winding a crank
- turning or shaking the device itself
One can also distinguish the extent to which energy can be stored, and by which technique: a flywheel, a battery or a capacitor.
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[edit] Dyno torch
A dyno torch is a flashlight or pocket torch which stores energy in a flywheel. The user squeezes a handle to operate a small dynamo, supplying electrical current to a miniature incandescent bulb. Dyno torches were very popular in Europe during World War II[citation needed] because the electrical power supply to homes was not very reliable.
[edit] Dyno torch design
In the photo, the L-shaped handle spins a gear, which in turn spins the dark grey magnet mounted on a flywheel, seen on the left. The magnet induces an electrical current in the red copper winding, seen on the right. The current from the copper winding flows through the incandescent bulb filament (not shown). Because electrical power is only produced when the handle is squeezed, a switch is not needed. The flywheel makes sure the light is fairly constant, despite the fact that the power supply (the squeezing) is intermittent.
An alternative design for an LED torch includes a rechargeable battery or a capacitor, and may offer 15 minutes or more of illumination for 1 minute of charging, though could be rendered useless by failure of the battery.
[edit] Faraday flashlight
The Faraday flashlight is another design of a mechanically-powered flashlight sold via direct marketing campaigns beginning in 2002.
The Faraday flashlight contains a super capacitor and charging mechanism that uses induction to power a high-intensity white LED array. Simply shaking the light for about thirty seconds provides about five minutes of light. Shaking the unit for 10 to 15 seconds every 2 or 3 minutes as necessary permits the device to be used continuously. This particular design of flashlight is documented in US patent 6729744 and EP patent 1413037.
Inside the flashlight, a sliding magnet moves back and forth inside a solenoid, or a spool of copper wire. Current is induced through the loops in the copper wire to create a current per Faraday's law of induction. This charges a capacitor, which essentially acts as a short-term battery. To produce light, the capacitor powers an array of LEDs.
[edit] Other functions
Some mechanically powered flashlights include other functions and features beyond just a source of light. For example, certain models may have additional special operating modes, such as flashing red or yellow lights that can serve as a caution or warning to other people that might see the light. Some models include a loud electronic siren that can also help warn of danger, or assist in locating someone who is lost. There are also many models of mechanically powered flashlights that include a built-in AM/FM, weather or shortwave radio.
[edit] See also
[edit] External links
- Instructables: A homemade solenoid type dyno torch inside a TicTac box.
- Die Goldcap-Dynamolampe (in German) — converting a dyno torch to LED operation with capacitor storage
- [1] To see a 3rd party Video review of a Faraday Flashlight by ASOTVI www.asotv.info
